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United States Patent | 6,084,351 |
Kai ,   et al. | July 4, 2000 |
In a metal halide lamp which includes a discharge tube (2) retaining a fill of mercury and at least one metal halide added as a luminous material, an energy density of the arc discharge portion (3) represented by a product E.times.j is in the range of 70.0.ltoreq.E.times.j.ltoreq.150.0 (VA/mm.sup.3) where E=V/d, j=I/S, assuming that I is a lamp current in amperes with a lamp voltage of V volts applied between the paired discharge electrodes in a stable lighting condition of the lamp and that each of the electrodes has a tip face (1a, 1a') of which a cut area in section is S mm.sup.2 and the gap distance is d in millimeters, and thus a high luminous flux retention rate and high luminance of an arc discharge portion can be accomplished with a longer life of the lamp, suppressing a lamp voltage varying rate, and avoiding a change in color temperature, which remarkably improves additional merits when in utilization as a light source in various display apparatuses such as optical projection systems.
Inventors: | Kai; Makoto (Yawata, JP); Kaneko; Yuriko (Nara, JP); Takeda; Mamoru (Souraku-gun, JP) |
Assignee: | Matsushita Electric Industrial Co., Ltd. (Osaka-fu, JP) |
Appl. No.: | 923421 |
Filed: | September 4, 1997 |
Sep 06, 1996[JP] | 8-236350 | |
Mar 17, 1997[JP] | 9-062660 |
Current U.S. Class: | 313/634; 313/570; 313/571; 313/620; 313/642 |
Intern'l Class: | H01J 017/16; H01J 061/30; H01J 017/20; H01J 061/12 |
Field of Search: | 313/44,493,570,571,634,637,638,639-41,642,643,620,621,605,606,10-11,13,17-19,28 315/147,317,324,116,115,112,50,117 |
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